SIIIANT ISLES. GEOLOGY. 443 



capricious as those in Gariveilan. The beds of soft clayey 

 rock seem here also generally to lie in the immediate 

 vicinity of the trap. Among them are seen regularly 

 disposed and thin strata of siliceous schist, similar to those 

 which are found independently placed in Gariveilan, and 

 alternating with the softer beds without any regular order. 



Having explained the botryoidal appearance of sili- 

 ceous schist when describing Scalpa, it is unnecessary 

 to take further notice of it here. I may only observe 

 that it is very remarkable in some of the specimens 

 found in this place ; the surfaces of which, to the depth 

 of an inch, are sometimes found entirely composed of 

 spherules adhering but by small points of contact. The 

 analogy of the other indurated strata to those which occur 

 on the north-eastern shore of Sky must also be apparent ; 

 the pale varieties of the siliceous schist being evidently 

 th cherty substances resulting from the induration of 

 some of the lias beds, and the black strata being those 

 which are produced by similar changes in the shale. It 

 is equally evident that the stratified substances here found 

 are in every respect analogous, both to those of Sky and 

 to those of Egg, which occur in a similar situation under 

 a mass of trap. They must therefore be considered as 

 detached portions of the uppermost strata ; indicating, 

 together with those of Rasay, Sky, and Egg, a deposit, 

 either once more connected and subsequently deranged 

 by the intrusion of trap ; or else perhaps connected, even 

 at the present moment, by intermediate portions beneath 

 the sea.* 



There is some difficulty in explaining the variety in 

 point of induration which is here to be observed among 

 substances, of which the composition is apparently the 

 same, and the position, with respect to the trap, identical. 

 It is not however peculiar to this place, as the same 

 differences occur under the same circumstances in Sky 



* Plate XXXII. fig. 3. 



